BUG REPORT: When using NetBackup 7.0.1, skewed or lower deduplication rates for full VMDK backups can be identified when comparing to guest level backups with a NetBackup client.

Article:TECH141946  |  Created: 2010-10-14  |  Updated: 2010-10-19  |  Article URL http://www.symantec.com/docs/TECH141946
Article Type
Technical Solution


Issue



After repeated VMDK backups, the deduplication ratio revealed in the job details is not what is expected.  Usually, this means the ratio is lower than expected.


Error



Here is an example from Job Details displaying the deduplication rate for a backup:

Sep 10, 2010 3:17:57 AM - Info myhost (pid=19056)
StorageServer=PureDisk:myhost; Report=PDDO Stats for (myhost): scanned: 6854265 KB, stream rate: 42.12 MB/sec, CR sent: 2783448 KB, dedup: 59.4%, cache hits: 23864 (44.6%)

 Observation of consecutive backups may reveal unusual or unexpected patterns in the dedup ratio.


Solution



Please contact Symantec technical support, referencing this document ID and Etrack 2158839 to obtain a Emergency Engineering Binary (EEB) package which contains a fix for this issue.

Note: This fix will only improve performance of VMDK backups to media servers with architectures where little-endian addressing is used by the operating system (for example, Windows, Linux on most architectures and others).  A fix for big-endian architectures and operating systems (for example, AIX, HP-UX, zLinux and others) is not available at this time.

This fix incudes improvements that align the deduplication with the filesystem and blocks stored in the VMDK image, leading to higher and more consistent deduplication results.

 


ETA of Fix:
Symantec has acknowledged that the above mentioned issue (Etrack 2139675) is present in the current version(s) of the product(s) mentioned at the end of this article.  Symantec is committed to product quality and satisfied customers.  This issue was scheduled to be addressed in the following release:

  • NetBackup 7.1

When NetBackup 7.1 is released, please visit the following link for download and readme information:
 http://www.symantec.com/business/support/index?page=landing&key=15143

Please note that Symantec Corporation reserves the right to remove any fix from the targeted release if it does not pass quality assurance tests or introduces new risks to overall code stability. Symantec's plans are subject to change and any action taken by you based on the above information or your reliance upon the above information is made at your own risk.

 

 


Supplemental Materials

SourceETrack
Value2139675
Description

[FID2888]DeDupe ratio is very low for VMWare VM's consecutive backup



Article URL http://www.symantec.com/docs/TECH141946


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